We calculate the splitting between fermion and anti-fermion effective masses
in high temperature gauge theories in the presence of a non-vanishing chemical
potential due to the CP-asymmetric fermionic background. In particular we
consider the case of left-handed leptons in the SU(2)⊗U(1) theory when
the temperature is above 250 GeV and the gauge symmetry is restored.Comment: 13 pages, TIPAC-93001